Smart cards are small electronic devices that resemble a credit card in size but contain an embedded microprocessor to store and process information. The class of devices known as “smart cards” includes smart cards, PCMCIA cards (or PC cards) and POD modules. PCMCIA stands for Personal Computer Memory Card International Association, a California nonprofit trade association created to standardize the connection of peripherals to portable computers. POD stands for “Point of Deployment” and refers to modules that are installed in electronic devices at the point of deployment to augment the functionality of the deployed device. As used herein, and in the appended claims, the term “smart card” will be used to refer collectively to smart cards, PCMCIA cards, PC cards, POD modules and any similar device that provides processing functionality provided in a card or card-like package.
Smart cards can be used for a wide variety of purposes. Some smart cards are used as intelligent credit or debit cards. PCMCIA or PC cards provide a lightweight, removable module that can be connected to a desktop computer, laptop computer, personal digital assistant or palm-top computer or other computerized device to provide additional programming and functionality for that computer or device.
An application of smart cards or POD modules that is of particular interest is the use of smart cards to control subscriber access to the services and programming provided over a cable television network.
Cable television systems allow subscribers access to dozens or even hundreds of channels of television programming. This wide variety of programming accounts for the great popularity of cable television. Additionally, the current trend is for cable television systems to provide additional services such as premium channels, pay-per-view programming, video-on-demand programming, Internet access and basic telephony.
In advanced cable television systems, each subscriber is typically provided with a set-top terminal. The set-top terminal is a box of electronic equipment that is used to connect the subscriber's television, or other electronic equipment, to the cable television system. The set-top terminal processes the signal received from the cable television system to provide the services of the cable system to subscribers.
As the premium services of the cable television system expand, security techniques for those premium services become crucial to ensure that only subscribers who have paid for the premium services have access to them. For example, premium channels, such as some movie channels, are scrambled before transmission to prevent unauthorized reception and viewing of those channels. Subscribers who pay additional fees to receive the premium channel or channels are provided with the means to descramble and view the premium channel or channels.
There are many techniques for controlling the remote descrambling of scrambled television signals. Typically a system subscriber who has paid to receive the scrambled premium channel or channels is provided with a descrambler unit that is connected between the source of the television signal source (e.g., a cable feed or a satellite receiver) and the subscriber's television set. While this descrambler unit may be a self-contained unit, descrambling circuitry is frequently and preferably incorporated into the subscriber's set-top terminal.
Unfortunately, proprietary algorithms used by descrambling circuitry can frequently, with enough effort, be “broken” or duplicated by an unauthorized party. Thereafter, unauthorized means of descrambling the cable system's premium channels might be made available to subscribers. To avoid this, the operator of the cable system may need to periodically change the proprietary algorithm used to scramble and descramble premium channels.
If the subscriber's descrambling circuitry is incorporated in a set-top terminal, the old descrambling circuitry must be removed and new descrambling circuitry inserted. To facilitate this process, removable modules that carry the descrambling circuitry can be provided to plug into a port of the set-top box. These removable modules are typically formed as smart cards or POD modules.
When the descrambling circuitry is to be changed or upgraded, the old module can be pulled from the set-top box, and a new module with the new circuitry or programming is installed in the set-top box. Thus, the set-top box can be upgraded without replacing the entire box. In addition to changing or upgrading the security features of the set-top box, other upgraded services that the box cannot currently provide can be provided on a smart card or POD module and installed to upgrade the set-top box without having to replace it entirely.
Smart cards, like those described above, typically have a programmable circuit that can be programmed with the functionality the card is designed to provide, for example, the proprietary algorithm used by a set-top box for decrypting or descrambling purposes. This programmability makes smart cards very adaptable and useful for a wide variety of purposes.
Smart cards may incorporate firmware programming to perform certain tasks. More sophisticated smart cards incorporate memory devices in which data and/or programming is stored. A programmable circuit in such a smart card may typically include a non-volatile Static Random Access Memory (SRAM) chip in which data or programming can be stored. Alternatively, more complex smart cards require the capacity and features of volatile memory. Volatile memory has advantages over non-volatile memory, but must have a constant source of power to maintain the data or programming stored therein.
Consequently, where volatile memory is used in a smart card, it becomes necessary to provide a power source to maintain the volatile memory. When the card is installed in a computer or computerized device, the volatile memory in the card can draw power from that host device. However, before the card is installed, or if the card is removed and stored, or re-installed in another host device, there may be difficulty in providing power to volatile memory.
To address these problems, it has been known to incorporate a single, small battery in the smart card to provide power to the on-board volatile memory. However, because of obvious size constraints, such battery power is of very limited capacity. This poses serious problems when the card is manufactured, programmed and may then spend as much as two years in storage before deployment in a host device.
Consequently, there is a need in the art for a system and method of providing power to a programming volatile memory on-board a smart card, particularly during an extended storage period between programming and deployment.